Provided herein are devices and processes for transfer printing of semiconductors. More specifically the devices relate to a tool apparatus for transfer printing semiconductor elements with high transfer printing yield and placement accuracy.
Semiconductor chip or die automated assembly equipments typically rely on the use of vacuum operated placement heads often referred to as vacuum grippers or pick-and-place tools. In their simplest embodiment, these placement heads typically consist of an open ended cylinder having a drilled nozzle surface which seals to the die to accomplish physical attachment. Semiconductor chips or die which are ultra thin, fragile, or too small cannot be economically handled by traditional vacuum grippers. As a result, alternative approaches such as self-assembly or dry transfer printing technologies are being investigated.
Transfer printing enables the massively parallel assembly of semiconductor devices, including for example, high performance semiconductor devices, onto virtually any substrate material, including glass, plastics, metals or other semiconductors (see, e.g., U.S. patent application Ser. No. 11/145,574 METHODS AND DEVICES FOR FABRICATING AND ASSEMBLING PRINTABLE SEMICONDUCTOR ELEMENTS filed Jun. 2, 2005). This semiconductor transfer printing technology relies on the use of a microstructured elastomeric stamp to selectively pick-up devices from a source wafer and then prints these devices onto a receiving substrate. The transfer process is massively parallel as the stamps are designed to transfer hundreds to thousands of discrete structures in a single pick-up and print operation.
While pick-and-place tools rely on suction forces, dry transfer printing tools rely on surface adhesion forces to control the pickup and release of the semiconductor devices. To enable dry transfer printing, methods to control the adhesion of semiconductor elements to an elastomeric stamp are required. One such method is described in U.S. patent application Ser. No. 11/423,192 filed Jun. 9, 2006 titled “PATTERN TRANSFER PRINTING BY KINETIC CONTROL OF ADHESION TO AN ELASTOMERIC STAMP.” In that method, the adhesion of the semiconductor elements to the stamp is controlled by adjusting the delamination rate of the elastomeric transfer stamp. This control of separation or delamination rate provides a means of increasing the pickup yield of semiconductor elements from a source wafer. This technique has been successfully used for bulk (single component) or thick (i.e. >1 mm) elastomeric stamps. There are, however, challenges with that technique for use with high fidelity, thin, (e.g., <1 mm) composite stamps. Composite stamps optimized for dry transfer printing semiconductor elements with high placement accuracy typically use high stiffness reinforcement materials as described in U.S. patent application Ser. No. 12/177,963, filed Jul. 23, 2008 titled “REINFORCED COMPOSITE STAMP FOR DRY TRANSFER PRINTING OF SEMICONDUCTOR ELEMENTS.” Those composite stamps can be used with a shear-assisted method to control the release yield of the semiconductor elements to a receiving substrate as described in U.S. Pat. App. No. 61/116,136 filed Nov. 19, 2008 titled “PRINTING SEMICONDUCTOR ELEMENTS BY SHEAR-ASSISTED ELASTOMERIC STAMP TRANSFER.” However, to date, no apparatus are currently capable of handling this new class of reinforced composite stamps while providing kinetic and shear-assisted control of adhesion.
Accordingly, there is a need for a novel tool apparatus to enable precise control of this novel class of reinforced composite stamps and achieve transfer printing semiconductor elements with high transfer printing yield and placement accuracy.